I've got a few mature box turtles. They weren't in the best shape when I got them, and this has been the first year that I let them hibernate outside. They hibernated in their enclosure, a wood box built 3x4 feet and about 2 feet tall. It's filled with bark and has a pond built out of a dishwashing pan. They seem pretty happy in it. Anyways, my smallest female had some shell rot when I got her. Their enclosure was in a shed this winter, so it wasn't wet. I didn't water the bark down during the winter to avoid getting the area too damp. Her shell rot is worse now, with a spot on her side, rump, and in the front near her chin. It doesn't look nasty, but I don't want it to get worse. Any ideas on how to treat it?